Caption: Close-up of the eye of a patient undergoing laser surgery. This is a technique which is used to treat disorders such as myopia, astigmatism and hypermetropia. The laser employed is called excimer (excited dimer) and uses a rare halide gas which is made of argon and fluorine. These disorders are corrected by re-shaping the cornea. The laser technique is an alternative to the conventional surgical technique known as radial keratomy. However, the use of the laser is still controversial. Possible adverse effects include the view of a ghost image for a period after the treatment and an increased opacity of the cornea.